Heretofore, as an inorganic solvent-free ordinary temperature curable coating composition excellent in weather resistance and heat resistance, a solvent-free ordinary temperature curable organosiloxane composition (Patent document 1), an organosiloxane liquid composition (Patent document 2) and the like are known. These are coating compositions capable of providing a coating film excellent in heat resistance and weather resistance, and in terms of flex resistance (deflection resistance), they are supposed to endure bending around a round bar with a shaft diameter of 3 mm or 10 mm. However, this was determined at the time when the material age was 5 to 7 days at 25° C. The curing thereof proceeds further as time proceeds, and in an accelerated weather resistance test or a humidity and cool-heat cycling test, significant cracks are formed in the coating film and they have poor crack resistance. Further, they have poor alkali resistance against a strong alkali at pH 12 or above.
Further, as a solvent-free ordinary temperature curable coating composition, a solvent-free two-liquid type ordinary temperature curable liquid polymer composition (Patent document 3) is known. Although this composition is excellent in crack resistance, it has poor weather resistance because it contains an acrylic resin at 12 to 22% by mass, and also it has poor anti-graffiti property and removability of graffiti.
Further, in the above Patent documents 1 to 3, there is no suggestion of a coating composition capable of forming a coating film with removability of graffiti.
On the other hand, organopolysiloxane curable compositions (Patent document 4 and Patent document 5) are also known as an inorganic ordinary temperature curable coating composition excellent in crack resistance and stain resistance. However, it is obvious from Examples and the like that either of them contains a solvent upon coating, and they are different in terms of the technical idea that a solvent-free type is provided in order to reduce the environmental burden and decrease the influence thereof on the human body and health as much as possible at which the present invention aims.
Patent document 1: Japanese Patent No. 2137192
Patent document 2: Japanese Patent No. 2774235
Patent document 3: Japanese Patent No. 3263331
Patent document 4: JP-A-2000-63612
Patent document 5: JP-A-2003-238895